The present invention relates to a voice coil motor actuator which performs the positioning operation of a magnetic head in order to record and reproduce information on and from a magnetic disk in a magnetic disk device and, more particularly, to a voice coil motor actuator for performing the positioning operation upon a pivot motion.
Of magnetic disk devices each performing the positioning operation of a magnetic head by a voice coil motor (VCM) actuator in order to record and reproduce information on and from a magnetic disk, a general magnetic disk device mounted with a voice coil actuator which performs the positioning operation upon a pivot or swing motion is shown in FIG. 3. Referring to FIG. 5, in a magnetic disk device 1, a slider 5 including a magnetic head is mounted on the distal end of a positioner 4 in order to record and reproduce information on and from a magnetic disk 2 which rotates together with a spindle motor 3. A coil 8 which constitutes a VCM actuator 6 is coupled to the proximal end of the positioner 4, and a magnet 7 is fixed to oppose the coil 8. A current is supplied to the coil 8 to perform a pivot motion about a pivot bearing shaft 9 of the coil 8 and the positioner 4, thereby positioning the slider 5 with respect to the magnetic disk 2.
The coil 8 of the conventional pivot (swing) VCM actuator 6 has an almost trapezoidal shape when viewed from the top, as shown in FIG. 6. Effective length portions 10 on the two sides of the trapezoidal shape which operate together with the magnet 7 to generate the driving force of the positioner 4 are almost parallel. Therefore, an effective length portion intersection 10a as an intersection between the extended lines of the effective length portions 10 is located on a side opposite to the coil 8 with respect to the pivot bearing shaft 9 serving as the center of the pivot motions of the coil 8 and the positioner 4.
As described above, in the conventional swing VCM actuator, the effective length portion intersection 10a of the coil 8 is located on the side opposite to the coil 8 with respect to the pivot bearing shaft 9. For this reason, when a rotation torque is generated by the VCM actuator 6, an external force other than this rotation torque acts on the pivot bearing shaft 9, resulting in increases in unnecessary vibration and noise.